Light-emitting diodes generally emit light in a specific color or range of wavelengths. To produce a white light, it is usually necessary to combine or mix the light from plural LEDs which emit different colors, for example, red, green and blue. Initially, light mixing was accomplished by placing LEDs of different colors next to each other such that the light emitted by each LED would mix with the light from the others. A common structure associated with such mixing is a light guide.
This approach has several drawbacks including poor color mixing, uneven light intensity, and the presence of dark regions near the edges of the light guide plate.
Several techniques have been made to improve the light mixing needed to produce which light. One is the insertion of the LEDs into a mixing cavity within the light guide. Another is the use of a light diffusor to mix the colors. While these techniques have resulted in slightly better color mixing, there remains a need for further improvement.